Innate lymphoid cell disturbance with increase in ILC1 in systemic lupus erythematosus

The SLE Conundrum: A Comprehensive Analysis of Pathogenesis, Recent Developments, and the Future of Therapeutic Interventions

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder with multifactorial interactions among various susceptibility factors. Significant strides have been made in understanding the pathogenesis of SLE, leading to the development of targeted therapies and the exploration of alternative treatments. The approval of new therapies has expanded patient treatment options, and ongoing clinical trials promise to enhance the treatment landscape further. The future of SLE treatment lies in personalized, targeted therapies that minimize side effects and improve patient outcomes. This review comprehensively analyzes SLE's current status and prospects based on recent studies, patents, clinical trials, and formulations. Continued research and clinical trials are crucial to uncovering new therapeutic options and ultimately transforming the treatment landscape for SLE. With sustained efforts and advancements in medical science, we can offer a better quality of life and improved survival rates for SLE patients.

ILC1 as critical gatekeepers in autoimmune kidney damage

A recent article has shown that blocking NKp46 signaling reduces injury, highlighting these cells as key drivers of organ damage and potential therapeutic targets in autoimmune diseases. In lupus nephritis, NKp46+ ILC1s orchestrate kidney inflammation by producing CSF2, driving the expansion of pro-inflammatory macrophages that infiltrate epithelial niches and exacerbate tissue damage.

Current cell therapies for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease in which multiple organs are damaged by the immune system. Although standard treatment options such as hydroxychloroquine (HCQ), glucocorticoids (GCs), and other immunosuppressive or immune-modulating agents can help to manage symptoms, they do not offer a cure. Hence, there is an urgent need for the development of novel drugs and therapies. In recent decades, cell therapies have been used for the treatment of SLE with encouraging results. Hematopoietic stem cell transplantation, mesenchymal stem cells, regulatory T (Treg) cell, natural killer cells, and chimeric antigen receptor T (CAR T) cells are advanced cell therapies which have been developed and evaluated in clinical trials in humans. In clinical application, each of these approaches has shown advantages and disadvantages. In addition, further studies are necessary to conclusively establish the safety and efficacy of these therapies. This review provides a summary of recent clinical trials investigating cell therapies for SLE treatment, along with a discussion on the potential of other cell-based therapies. The factors influencing the selection of common cell therapies for individual patients are also highlighted.

The role of innate lymphoid cells in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a connective tissue disorder that affects various body systems. Both the innate and adaptive immunity contribute to the onset and progression of SLE. The main mechanism of SLE is an excessive immune response of immune cells to autoantigens, which leads to systemic inflammation and inflammation-induced organ damage. Notably, a subset of innate immune cells known as innate lymphoid cells (ILCs) has recently emerged. ILCs are pivotal in the early stages of infection; participate in immune responses, inflammation, and tissue repair; and regulate the immune function of the body by resisting pathogens and regulating autoimmune inflammation and metabolic homeostasis. Thus, ILCs dysfunction can lead to autoimmune diseases. This review discusses the maturation of ILCs, the potential mechanisms by which ILCs exacerbate SLE pathogenesis, and their contributions to organ inflammatory deterioration in SLE.

Innate lymphoid cell subsets in the pathogenesis of primary biliary cholangitis

BACKGROUND AND AIM

Primary biliary cholangitis (PBC) is an autoimmune liver disease characterized by destructive lymphocytic cholangitis and specific anti-mitochondrial antibodies. Innate lymphoid cells (ILCs) have been reported to play a role in liver homeostasis and autoimmunity.

METHODS

We evaluated the features of peripheral ILC1s and ILC3 in patients with PBC and hepatic ILC1 and ILC3 in two different PBC mouse models (dominant-negative transforming growth factor-beta receptor II [dnTGFβRII] and 2-octynoic acid-bovine serum albumin [2OA-BSA]).

RESULTS

A total of 115 patients and 18 healthy controls were enrolled in the study. Decreased circulating ILC1/3s were observed in early-stage PBC patients, and the numbers of ILC1/3s were negatively correlated with specific parameters and the proportion of T-helper (Th) 1 and Th17 cells. Reduced numbers of ILC1s were observed in PBC mouse models with different etiologies. ILC1-deficient mice had more severe hepatic inflammation after inducing the 2OA-BSA model. Continuous low-dose injections of lipopolysaccharide (LPS) reduced ILC1 levels in mice, consistent with the lower level of ILC1s in PBC patients with high LPS (> 50 ng/mL), and aggravated hepatic lymphocyte infiltration.

CONCLUSION

Patients with PBC had decreased ILC1s, which were negatively correlated with CD4+ T cells. Deficient ILC1 populations led to disease exacerbations in mice. Our results indicated that ILC1s may participate in the pathogenesis of PBC.

The role of the aryl hydrocarbon receptor (AhR) in modulating intestinal ILC3s to optimise gut pathogen resistance in lupus and benefits of nutritional AhR ligands

BACKGROUND AND AIMS

Dysbiosis is emerging as a potential trigger of systemic lupus erythematosus (SLE). Group 3 innate lymphoid cells (ILC3s) are recognised as key regulators of intestinal homeostasis. The aryl hydrocarbon receptor (AhR) is critical to intestinal ILC3 development and function. This mechanistic review aimed to investigate whether AhR activation of gut ILC3s facilitates IL-22-mediated antimicrobial peptide (AMP) production to enhance colonisation resistance and ameliorate SLE pathology associated with intestinal dysbiosis. Furthermore, nutritional AhR ligand potential to enhance pathogen resistance was explored.

METHODOLOGY

This mechanistic review involved a three-tranche systematic literature search (review, mechanism, intervention) using PubMed with critical appraisal. Data was synthesised into themes and summarised in a narrative analysis.

RESULTS

Preclinical mechanistic data indicate that AhR modulation of intestinal ILC3s optimises pathogen resistance via IL-22-derived AMPs. Pre-clinical research is required to validate this mechanism in SLE. Data on systemic immune consequences of AhR modulation in lupus suggest UVB-activated ligands induce aberrant AhR signalling while many dietary ligands exert beneficial effects. Data on xenobiotic-origin ligands is varied, although considerable evidence has demonstrated negative effects on Th17 to Treg balance. Limited human evidence supports the role of nutritional AhR ligands in modulating SLE pathology. Preclinical and clinical data support anti-inflammatory effects of dietary AhR ligands.

CONCLUSION

Current evidence is insufficient to fully validate the hypothesis that AhR modulation of intestinal ILC3s can enhance pathogen resistance to ameliorate lupus pathology driven by dysbiosis. However, anti-inflammatory effects of dietary AhR ligands suggest a promising role as a therapeutic intervention for SLE.

Deep immunophenotyping reveals that autoimmune and autoinflammatory disorders are spread along two immunological axes capturing disease inflammation levels and types

OBJECTIVES

Based on genetic associations, McGonagle and McDermott suggested a classification of autoimmune and autoinflammatory diseases as a continuum ranging from purely autoimmune to purely autoinflammatory diseases and comprising diseases with both components. We used deep immunophenotyping to identify immune cell populations and molecular targets characterising this continuum.

METHODS

We collected blood from 443 patients with one of 15 autoimmune or autoinflammatory diseases and 71 healthy volunteers. Deep phenotyping was performed using 13 flow cytometry panels characterising over 600 innate and adaptive cell populations. Unsupervised and supervised analyses were conducted to identify disease clusters with their common and specific cell parameters.

RESULTS

Unsupervised clustering categorised these diseases into five clusters. Principal component analysis deconvoluted this clustering into two immunological axes. The first axis was driven by the ratio of LAG3+ to ICOS+ in regulatory T lymphocytes (Tregs), and segregated diseases based on their inflammation levels. The second axis was driven by activated Tregs and type 3 innate lymphoid cells (ILC3s), and segregated diseases based on their types of affected tissues. We identified a signature of 23 cell populations that accurately characterised the five disease clusters.

CONCLUSIONS

We have refined the monodimensional continuum of autoimmune and autoinflammatory diseases as a continuum characterised by both disease inflammation levels and targeted tissues. Such classification should be helpful for defining therapies. Our results call for further investigations into the role of the LAG3+/ICOS+ balance in Tregs and the contribution of ILC3s in autoimmune and autoinflammatory diseases.

TRIAL REGISTRATION NUMBER

NCT02466217.

Group 3 Innate Lymphoid Cells Exacerbate Lupus Nephritis by Promoting B Cell Activation in Kidney Ectopic Lymphoid Structures

Group 3 innate lymphoid cells (ILC3s) represent a new population in immune regulation, yet their role in lupus nephritis (LN) remains elusive. In the present work, systemic increases in ILC3s, particularly in the kidney, are observed to correlate strongly with disease severity in both human and murine LN. Using MRL/lpr lupus mice and a nephrotoxic serum-induced LN model, this study demonstrates that ILC3s accumulated in the kidney migrate predominantly from the intestine. Furthermore, intestinal ILC3s accelerate LN progression, manifested by exacerbated autoimmunity and kidney injuries. In LN kidneys, ILC3s are located adjacent to B cells within ectopic lymphoid structures (ELS), directly activating B cell differentiation into plasma cells and antibody production in a Delta-like1 (DLL1)/Notch-dependent manner. Blocking DLL1 attenuates ILC3s' effects and protects against LN. Altogether, these findings reveal a novel pathogenic role of ILC3s in B cell activation, renal ELS formation and autoimmune injuries during LN, shedding light on the therapeutic value of targeting ILC3s for LN.

ILC3: a case of conflicted identity

Innate lymphoid cells type 3 (ILC3s) are the first line sentinels at the mucous tissues, where they contribute to the homeostatic immune response in a major way. Also, they have been increasingly appreciated as important modulators of chronic inflammatory and autoimmune responses, both locally and systemically. The proper identification of ILC3 is of utmost importance for meaningful studies on their role in immunity. Flow cytometry is the method of choice for the detection and characterization of ILC3. However, the analysis of ILC3-related papers shows inconsistency in ILC3 phenotypic definition, as different inclusion and exclusion markers are used for their identification. Here, we present these discrepancies in the phenotypic characterization of human and mouse ILC3s. We discuss the pros and cons of using various markers for ILC3 identification. Furthermore, we consider the possibilities for the efficient isolation and propagation of ILC3 from different organs and tissues for in-vitro and in-vivo studies. This paper calls upon uniformity in ILC3 definition, isolation, and propagation for the increased possibility of confluent interpretation of ILC3's role in immunity.

Elevation of Metrnβ and Its Association with Disease Activity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an auto-immune disease, the pathogenesis of which remains to be fully addressed. Metrnβ is a novel cytokine involved in the pathogenesis of inflammatory disease, but its regulatory roles in SLE are unclear. We aimed to comprehensively investigate the clinical value of Metrnβ in SLE. A massive elevation of circulating Metrnβ levels was observed in SLE, and patients with an active phase displayed higher Metrnβ concentrations than those with inactive phases. Additionally, we found that Metrnβ expression was positively correlated with clinical indicators of SLE. Longitudinal cytokine and chemokine profiles revealed a disturbed immune response in SLE, with high activity profiles displayed severe pathogenic inflammation, and a positive correlation of the serum Metrnβ with CXCL9, IL10, IL18 and IL1RA was observed as well. Moreover, Metrnβ expressions exhibited an inverse correlation with Treg and B10. Of note, a significant decrease of ILC2 was found in SLE, and there was a negative correlation of Metrnβ with ILC2 as well. Further ROC analysis showed that the area under the curve (AUC) for Metrnβ was 0.8250 (95% CI: 0.7379-0.9121), with a cutoff value of 1131 pg/mL to effectively distinguish SLE patients from healthy controls. Our study herein demonstrated for the first time that Metrnβ values were increased and were immunologically correlated with SLE activity, which could be utilized as an alternative biomarker for the early identification and predicting of the immuno-response of SLE.

The enrichment of Arg1+ILC2s and ILCregs facilitates the progression of endometriosis: A preliminary study

Innate lymphoid cells (ILCs) are a kind of lymphocytes that reside in the tissue and have an essential function in the immune microenvironment. However, the relationship between endometriosis (EMS) and ILCs is complex and not fully understood. This study examines several groups of ILCs in the peripheral blood (PB), peritoneal fluid (PF) and endometrium of patients with EMS via flow cytometry. The study observed an increase in PB ILCs, particularly ILC2s and ILCregs subsets and Arg1+ILC2s in the EMS patients were highly activated. EMS patients had significantly higher levels of serum interleukin (IL)-10/33/25 compared to controls. We also found an elevation of Arg1+ILC2s in the PF and higher levels of ILC2s and ILCregs in ectopic endometrium compared with eutopic. Importantly, a positive correlation was observed between the enrichment of Arg1+ILC2s and ILCregs in the PB of EMS patients. The findings indicate that the involvement of Arg1+ILC2s and ILCregs fosters potentially endometriosis progression.

Association of interleukin 33 gene polymorphisms with susceptibility and regulation of inflammatory mediators in Systemic lupus erythematosus patients

BACKGROUND

Studies have indicated the involvement of interleukin (IL)-33 in the pathogenesis of Systemic lupus erythematosus (SLE). This research intended to evaluate the association of IL33 gene rs1929992 and rs7044343 Single nucleotide polymorphisms (SNPs) with risk of SLE. In addition, the association between these SNPs and inflammatory cytokines was determined.

METHODS

In this study, 200 SLE cases and 200 healthy subjects were recruited. Using allelic discrimination Real-time PCR, IL33 gene rs1929992 and rs7044343 SNPs were genotyped. The mRNA expression levels of IL-1β, IL-6, IL-33, TNF-α were determined in the peripheral blood mononuclear cells (PBMCs). The serum levels of cytokines were also measured.

RESULTS

The G allele (OR = 1.57, CI: 1.18-2.08, P = 0.0017), GG genotype (OR = 2.52, CI: 1.33-4.77, P = 0.0043), and GA genotype (OR = 2.12, CI: 1.34-3.34, P = 0.0011) of rs1929992 SNP was significantly associated with an increased SLE risk. The C allele (OR = 1.44, CI: 1.08-1.90; P = 0.0105), CC genotype (OR = 2.07, CI: 1.15-3.71; P = 0.0146), and CT genotype (OR = 1.61, CI: 1.02-2.53, P = 0.0395) of rs7044343 was significantly associated with increased SLE risk. The PBMC mRNA expression and serum levels of IL-1β, IL-6, IL-33, TNF-α were significantly increased in the SLE patients compared to controls. However, there was no significant difference in the mRNA expression and serum levels of IL-1β, IL-6, IL-33, and TNF-α among the SLE patients with three genotypes for both rs1929992 and rs7044343 polymorphisms.

CONCLUSIONS

IL33 gene rs1929992 and rs7044343 SNPs are involved in SLE pathogenesis but they might not influence on the inflammatory pathway.

Involvement of ILC1-like innate lymphocytes in human autoimmunity, lessons from alopecia areata

Here, we have explored the involvement of innate lymphoid cells-type 1 (ILC1) in the pathogenesis of alopecia areata (AA), because we found them to be significantly increased around lesional and non-lesional HFs of AA patients. To further explore these unexpected findings, we first co-cultured autologous circulating ILC1-like cells (ILC1lc) with healthy, but stressed, organ-cultured human scalp hair follicles (HFs). ILClc induced all hallmarks of AA ex vivo: they significantly promoted premature, apoptosis-driven HF regression (catagen), HF cytotoxicity/dystrophy, and most important for AA pathogenesis, the collapse of the HFs physiological immune privilege. NKG2D-blocking or IFNγ-neutralizing antibodies antagonized this. In vivo, intradermal injection of autologous activated, NKG2D+/IFNγ-secreting ILC1lc into healthy human scalp skin xenotransplanted onto SCID/beige mice sufficed to rapidly induce characteristic AA lesions. This provides the first evidence that ILC1lc, which are positive for the ILC1 phenotype and negative for the classical NK markers, suffice to induce AA in previously healthy human HFs ex vivo and in vivo, and further questions the conventional wisdom that AA is always an autoantigen-dependent, CD8 +T cell-driven autoimmune disease.

The dysregulation of circulating innate lymphoid cells is related to autoantibodies in pemphigus vulgaris

BACKGROUND

Pemphigus vulgaris (PV) is a typical autoimmune disease caused by autoantibodies. Innate lymphoid cells (ILCs) are non-antigen-dependent populations composed of different subsets, also known as "mirror cells" of T cells, which play a crucial role in immune inflammatory diseases. However, the characteristics of ILCs in PV are unclear.

METHODS

Patients diagnosed with PV along with healthy controls in Second Xiangya Hospital of Central South University were studied. Flow cytometry was used to detect the proportion of ILC subsets in the peripheral blood. Anti-desmoglein (DSG) 1 and anti-DSG3 antibody levels of PV patients were detected.

RESULTS

Thirty-eight PV patients and 37 healthy controls were enrolled. There were no differences in sex or age between the two groups. Compared with controls, ILCs/CD45⁺ lymphocytes were significantly decreased in patients with PV. The frequency of ILC1s increased in patients with PV and was positively correlated with anti-DSG3 antibodies. However, the frequency of ILC3s decreased in patients with PV and was negatively correlated with anti-DSG1 antibodies. After methylprednisolone treatment, ILC1/ILC levels significantly decreased.

CONCLUSIONS

Circulating ILC subsets are associated with PV pathogenesis. Upregulated ILC1s seem to correlate positively with PV severity and can be restored after treatment.

Peripheral Eosinophil Count Associated with Disease Activity and Clinical Outcomes in Hospitalized Patients with Lupus Nephritis

INTRODUCTION

The aim of this study was to evaluate the association of peripheral eosinophil (EOS) count with disease activity and kidney outcomes in lupus nephritis (LN) patients.

METHODS

A total of 453 hospitalized and biopsy-proven LN patients at our hospital from 2006 to 2013 were enrolled, of which 388 patients had repeated measurements of EOS. Relationships were explored between average EOS and disease activity at baseline, using the systemic lupus erythematosus disease activity (SLEDAI) and activity index (AI) on kidney biopsy. Follow-up data were available through December 2016. The primary outcome measure was a composite of doubling of serum creatinine and end-stage kidney disease after a median follow-up of 51 months.

RESULTS

The mean age of the enrolled 388 LN patients was 33.1 ± 10.8 years old, and 335 (86%) were female. The median average peripheral EOS count was 0.033 (0.015-0.057) ×109/L. Mean AI and SLEDAI score were 6.8 ± 2.5 and 14.9 ± 5.4, respectively. Logistic regression models showed that decreased average EOS was independently associated with higher AI (≥6) and higher SLEDAI (≥15) (odds ratio [OR] 0.93, 95% confidence interval [CI] 0.90-0.97; and OR 0.96, 95% CI: 0.93-0.99, respectively). There was a parabolic relationship between average EOS and the primary outcome, with hazard ratio (HR) > 1 for both levels ≤0.033 and >0.16 × 109/L.

CONCLUSION

Lower EOS count was independently associated with severe disease activity and kidney progression in LN.

Imbalance of circulating innate lymphoid cell subpopulations in patients with chronic kidney disease

Innate lymphoid cells (ILCs) are a newly identified heterogeneous family of innate immune cells. We conducted this study to investigate the frequency of circulating ILC subsets in various chronic kidney diseases (CKD). In DN, the proportion of total ILCs and certain ILC subgroups increased significantly. Positive correlations between proportion of total ILCs, ILC1s and body mass index, glycated hemoglobin were observed in DN. In LN, a significantly increased proportion of ILC1s was found in parallel with a reduced proportion of ILC2s. The proportions of total ILCs and ILC1s were correlated with WBC count and the level of C3. In all enrolled patients, the proportion of total ILCs and ILC1s was significantly correlated with the levels of ACR and GFR. In the present study, the proportion of circulating ILC subsets increased significantly in various types of CKD and correlated with clinico-pathological features, which suggests a possible role for ILCs in CKD.

Increased circulating innate lymphoid cell (ILC)1 and decreased circulating ILC3 are involved in the pathogenesis of Henoch-Schonlein purpura

Background

Innate lymphoid cell (ILC) dysfunction is involved in numerous immune diseases, but this has not been demonstrated in Henoch-Schonlein purpura (HSP). This study aimed to investigate whether ILC dysfunction or imbalance participate in the pathogenesis of HSP.

Methods

This was a prospective study in patients with HSP who were hospitalized at the Children’s Hospital of Soochow University from June to December 2019. Age- and sex-matched controls were also enrolled. ILC subsets and lymphocyte subpopulations were determined by flow cytometry. The transmission immune turbidimetric method also facilitated the exploration of correlations between ILC subset frequency and lymphocyte subpopulation, as well as serum IgA in HSP patients.

Results

Fifty-one patients with HSP and 22 control patients were included. There were no differences in age and sex between the two groups. Compared with controls, patients with HSP had higher ILCs in relation to lymphocytes (P = 0.036), higher ILCs in relation to PBMCs (P = 0.026), higher ILC1s (P < 0.001), lower ILC3s (P < 0.05), and higher ILC1/ILC3 ratio (P < 0.001). Sixteen patients underwent routine therapy combined with methylprednisolone for 7–10 days; ILC1s were significantly decreased (P < 0.001) and ILC3s were increased (P = 0.033), and ILC1/ILC3 was significantly decreased (P < 0.001). Compared with the controls, the ratios of ILCs/lymphocytes and ILCs/PBMC were higher in patients in the arthritis and mixed groups (all P < 0.05). ILC1 were elevated in the purpura, arthritis, abdominal, and mixed groups (P = 0.027, P = 0.007, P < 0.001, and P < 0.001, respectively). ILC1/ILCs were positively correlated with CD3 + CD8 + T lymphocytes (r = 0.3701, P = 0.0075). The level of IgA did not correlate with ILCs.

Conclusions

Higher circulating ILC1s and lower circulating ILC3s appear to be involved in the pathogenesis of HSP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03262-w.

Imbalanced distribution of group 2 innate lymphoid cells (ILCs) and ILC precursors in peripheral blood of patients with primary biliary cholangitis

Innate lymphoid cells (ILCs), a novel group of innate immune cells, play a key role in the early immune response via rapidly reacting to signals expressed by tissue-resident cells. ILCs contribute to some autoimmune diseases. We aim to investigate the proportions of circulating ILC subgroups in patients with primary biliary cholangitis (PBC). Overall, 48 patients with PBC and 24 healthy controls (HCs) were enrolled. Circulating ILCs and cytokine production were detected by flow cytometry. The proportions of total ILCs, ILC precursors (ILCPs), and ILCP/ILC2 ratio increased and that of ILC2s decreased in patients with PBC. ILC2 proportion was negatively correlated with gamma-glutamyl transpeptidase (GGT), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). The proportion of ILCPs and ILCP/ILC2 ratio were positively correlated with alkaline phosphatase, GGT, ALT, and AST. ILC2 proportion was significantly decreased in the ursodeoxycholic acid (UDCA) -non-responder group compared with the UDCA-responder group, whereas the proportion of ILCPs and ILCP/ILC2 were ratio significantly increased. The proportions of CD38⁺ ILC2s, CD38⁺ ILCPs, CD45RO⁺ ILC2s, and CD45RO⁺ ILCPs were significantly higher in patients with PBC than in HCs. Levels of IL-17A producing ILCs were higher in patients with PBC than in HCs. PBC is accompanied by alterations in circulating ILCs. The proportions of ILC2s, ILCPs, and ILCP/ILC2 ratio were associated with the PBC disease activity. The proportions of ILCPs and ILCP/ILC2 ratio may reflect the UDCA treatment failure in patients with PBC. ILC2s and ILCPs from patients with PBC get activated, these cells may be involved in the pathogenesis of PBC.

Role of the innate and adaptive immune responses in the pathogenesis of systemic lupus erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE), the most common form of lupus, is a multisystemic rheumatic disease with different clinical features that generally affect women of childbearing age. The common symptoms of SLE are very similar to other autoimmune and non-autoimmune disorders, thereby it is known as a thousand faces disease. In this article, we are going to discuss some of the most updated information about immune system-related factors, cells, and cytokines involved in SLE pathogenesis.

METHODS

Different electronic databases, especially PubMed/MEDLINE, Scopus, and Google Scholar, were searched to review and analyze relevant literature on the role of innate and adaptive immune cells and cytokines in the pathogenesis of SLE. A search for relevant literature was accomplished using various keywords including systemic lupus erythematosus, apoptosis, autoantibodies, immunopathogenesis of SLE, adaptive and innate immune cells, inflammatory cytokines, hormones, etc. RESULTS AND CONCLUSION: The most important characteristic of SLE is the production of antibodies against different nuclear autoantigens like double-strand DNA and RNA. The depositions of the immune complexes (ICs) that are generated between autoantibodies and autoantigens, along with aberrant clearance of them, can lead to permanent inflammation and contribute to tissue or organ damage. Related mechanisms underlying the initiation and development of SLE have not been clarified yet. Although, defects in immune tolerance, enhanced antigenic load, hyperactivity of T cells, and inappropriate regulation of B cells contribute to the pathogenic autoantibodies generation. Besides, sex hormones that influence the immune system seem to act as triggers or protectors of SLE development.

Involvement of IL-33 in the Pathophysiology of Systemic Lupus Erythematosus: Review

IL-33 is a newly discovered cytokine displaying pleiotropic localizations and functions. More specifically, it also functions as an alarmin, following its release from cells undergoing cell death or necrosis, to alert the innate immune system. The role of IL-33 has been underlined in several inflammatory and autoimmune diseases including systemic lupus erythematosus (SLE). The expressions of IL-33 as well as its receptor, ST2, are significantly upregulated in SLE patients and in patients with lupus nephritis. This review discusses the involvement of IL-33 in the pathology of SLE.

Tissue-Dependent Adaptations and Functions of Innate Lymphoid Cells

Tissue-resident immune cells reside in distinct niches across organs, where they contribute to tissue homeostasis and rapidly respond to perturbations in the local microenvironment. Innate lymphoid cells (ILCs) are a family of innate immune cells that regulate immune and tissue homeostasis. Across anatomical locations throughout the body, ILCs adopt tissue-specific fates, differing from circulating ILC populations. Adaptations of ILCs to microenvironmental changes have been documented in several inflammatory contexts, including obesity, asthma, and inflammatory bowel disease. While our understanding of ILC functions within tissues have predominantly been based on mouse studies, development of advanced single cell platforms to study tissue-resident ILCs in humans and emerging patient-based data is providing new insights into this lymphocyte family. Within this review, we discuss current concepts of ILC fate and function, exploring tissue-specific functions of ILCs and their contribution to health and disease across organ systems.

Innate Lymphoid Cells in Autoimmune Diseases

Innate lymphoid cells (ILC) are a heterogeneous group of immune cells characterized by lymphoid morphology and cytokine profile similar to T cells but which do not express clonally distributed diverse antigen receptors. These particular cells express transcription factors and cytokines reflecting their similarities to T helper (Th)1, Th2, and Th17 cells and are therefore referred to as ILC1, ILC2, and ILC3. Other members of the ILC subsets include lymphoid tissue inducer (LTi) and regulatory ILC (ILCreg). Natural killer (NK) cells share a common progenitor with ILC and also exhibit a lymphoid phenotype without antigen specificity. ILC are found in low numbers in peripheral blood but are much more abundant at barrier sites such as the skin, liver, airways, lymph nodes, and the gastrointestinal tract. They play an important role in innate immunity due to their capacity to respond rapidly to pathogens through the production of cytokines. Recent evidence has shown that ILC also play a key role in autoimmunity, as alterations in their number or function have been identified in systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Here, we review recent advances in the understanding of the role of ILC in the pathogenesis of autoimmune diseases, with particular emphasis on their role as a potential diagnostic biomarker and as therapeutic targets.

The Tipped Balance of ILC1/ILC2 in Peripheral Blood of Oral Lichen Planus Is Related to Inflammatory Cytokines

Oral lichen planus (OLP) is an immune-inflammatory disease mediated by T cells. Innate lymphoid cells (ILCs) constitute a novel family of immune cells that initially originate from common innate lymphoid progenitors. Termed “T cells counterparts,” ILCs play a prominent role in inflammatory-immune diseases. However, the characterization of ILCs and their related induced factors were unclear in OLP. In the present study, the phenotypic characteristics of ILCs and their correlation with inflammatory cytokines were explored in the peripheral blood of OLP patients and healthy controls. We found that the proportion of total ILCs was expanded in OLP and was positively correlated with disease severity. The highly skewed distribution of ILC subpopulations was notable in OLP. Specifically, the frequency of ILC1s was significantly increased, while that of ILC2s was significantly reduced in total ILCs of OLP, resulting in the markedly elevated ILC1/ILC2 ratio in OLP. Correspondingly, ILCs in OLP displayed high expression of T-bet but low expression of GATA3. In addition, the IFN-γ expression level was elevated in ILC1s, whereas the IL-4 expression level was decreased in ILC2s. Moreover, ILC-associated activators IL-12, IL-18, and IL-1β were upregulated in OLP plasma, with IL-12 and IL-1β both positively correlated with the ILC1/ILC2 ratio. Further in vitro stimulation tests indicated that OLP plasma remarkedly increased the ILC1/ILC2 ratio, especially that IL-12 and IL-1β tipped the balance between ILC1s and ILC2s toward ILC1s in total ILCs. Overall, elevated levels of IL-12 and IL-1β might act as environmental cues in tipping the balance of ILC1/ILC2 in the peripheral blood of OLP, contributing to the immune dysregulation in OLP.

Phenotype, function and clinical significance of innate lymphoid cells in immunoglobulin G4-related disease

OBJECTIVE

Innate immune system participates in immunoglobulin G4 related disease (IgG4-RD). While the role of innate lymphoid cells (ILCs) in IgG4-RD remains to be elucidated, we aimed to evaluate the phenotype, function and clinical significance of ILCs in IgG4-RD patients.

METHODS

Sixty-seven untreated IgG4-RD patients, age and sex matched healthy controls (HCs) were enrolled. Circulating and tissue infiltration of ILCs were detected by flow cytometry. Serum suppression of tumorigenicity 2 (sST2) was detected by ELISA and membrane-bound ST2 (ST2L) was detected by flow cytometry. Tissue infiltration of IL-33 was measured by immunohistochemistry staining. RT-qPCR was performed to analyze the expression pattern of ILC2 associated genes between HCs and IgG4-RD patients. In addition, correlation analysis was performed in order to evaluate clinical significance of ILCs in IgG4-RD.

RESULTS

The frequency of circulating pan ILCs in IgG4-RD patients was lower than in HCs. ILC2s was higher in IgG4-RD compared with HCs, whereas ILC1s was lower in IgG4-RD. sST2 and ST2L were increased in IgG4-RD than HC. Infiltration of ILC1s in submandibular glands of IgG4-RD was more prominent than ILC2s. Intracellular secretion of IL-9 was increased in ILC2s of IgG4-RD than in HCs. Circulating ILC2s correlated positively with Treg cells, the surface expression of CD154, PD-1 and CXCR5 in ILC2s correlated positively with CD19+B cells, serum IgG4 level and serum IgE, respectively.

CONCLUSION

ILCs and their subsets were significantly altered in IgG4-RD. We demonstrated the dysfunction of ILC2s in IgG4-RD by phenotype, correlation analysis, and function investigation, revealing ILC2s participated in the pathogenesis of IgG4-RD.

IL-33 in Rheumatic Diseases

Interleukin-33 (IL-33) is a nuclear factor mainly expressed in barrier epithelium, endothelial cells, and fibroblast reticular cells. Some inflammatory cells also express IL-33 under certain conditions. The important role of IL-33 in allergic reactions, helminth infection, cancer, tissue fibrosis, chronic inflammation, organ transplantation, and rheumatic immune diseases has been extensively studied in recent years. IL-33 primarily activates various circulating and tissue-resident immune cells, including mast cell, group 2 innate lymphoid cell (ILC2), regulatory T cell (Treg), T helper 2 cell (Th2), natural killer cell (NK cell), and macrophage. Therefore, IL-33 plays an immunomodulatory role and shows pleiotropic activity in different immune microenvironments. The IL-33/serum stimulation-2 (ST2) axis has been shown to have a detrimental effect on rheumatoid arthritis, systemic lupus erythematosus, and other rheumatic diseases. Interestingly, IL-33 also plays a protective role in the repair of barrier epithelium and the activation of Tregs. Therefore, the role of IL-33/ST2 depends on the underlying pathological conditions in rheumatic diseases. This review focuses on the dual role of the IL-33/ST2 axis in rheumatic diseases.

Roles of IL-25 in Type 2 Inflammation and Autoimmune Pathogenesis

Interleukin-17E (IL-25) is a member of the IL-17 cytokine family that includes IL-17A to IL-17F. IL-17 family cytokines play a key role in host defense responses and inflammatory diseases. Compared with other IL-17 cytokine family members, IL-25 has relatively low sequence similarity to IL-17A and exhibits a distinct function from other IL-17 cytokines. IL-25 binds to its receptor composed of IL-17 receptor A (IL-17RA) and IL-17 receptor B (IL-17RB) for signal transduction. IL-25 has been implicated as a type 2 cytokine and can induce the production of IL-4, IL-5 and IL-13, which in turn inhibits the differentiation of T helper (Th) 17. In addition to its anti-inflammatory properties, IL-25 also exhibits a pro-inflammatory effect in the pathogenesis of Th17-dominated diseases. Here, we review recent advances in the roles of IL-25 in the pathogenesis of inflammation and autoimmune diseases.

Association of microRNA-125a with the clinical features, disease activity and inflammatory cytokines of juvenile-onset lupus patients

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with marked variation in its clinical presentation. Juvenile-onset SLE (jSLE) exhibits an aggressive clinical phenotype and severe complications. Dysregulated expression of microRNAs (miRs) in immune cells from patients with SLE has been found. We aim to evaluate the association of miR-125a with the clinical and laboratory characteristics, disease activity and inflammatory cytokines of jSLE patients.

METHODS

60 jSLE patients and 25 normal controls were involved in the study. The expression pattern of miR-125a was determined in plasma of all subjects using qRT-PCR. In addition, plasma levels of IL-17 and IFN-γ were examined using ELISA. The correlation of miR-125a expression with the clinical manifestations and disease activity of jSLE patients was analyzed. Also, its association with the inflammatory cytokines was investigated in jSLE patients.

RESULTS

Our findings showed that miR-125a expression levels were significantly reduced in jSLE patients compared to normal controls (p < 0.01) and these expression levels differed based on the clinical variability of patients. In addition, plasma levels of IL-17 and IFN-γ in jSLE patients were significantly higher than healthy controls (p < 0.01). Finally, miR-125a expression had significant negative associations with each of SLEDAI-2K (p < 0.01), SLICC (p < 0.01), ESR (p < 0.05), proteinuria (p < 0.01) and IL-17 levels (p < 0.01) in jSLE patients.

CONCLUSION

Our findings postulate that miR-125a could act as a candidate therapeutic target for its possible regulation of inflammation in jSLE patients.

The Role of the IL-33/ST2 Immune Pathway in Autoimmunity: New Insights and Perspectives

Interleukin (IL)-33, a member of IL-1 cytokine family, is produced by various immune cells and acts as an alarm to alert the immune system after epithelial or endothelial cell damage during cell necrosis, infection, stress, and trauma. The biological functions of IL-33 largely depend on its ligation to the corresponding receptor, suppression of tumorigenicity 2 (ST2). The pathogenic roles of this cytokine have been implicated in several disorders, including allergic disease, cardiovascular disease, autoimmune disease, infectious disease, and cancers. However, alerted levels of IL-33 may result in either disease amelioration or progression. Genetic variations of IL33 gene may confer protective or susceptibility risk in the onset of autoimmune diseases. The purpose of this review is to discuss the involvement of IL-33 and ST2 in the pathogenesis of a variety of autoimmune disorders, such as autoimmune rheumatic, neurodegenerative, and endocrine diseases.

The Expression of P2X7 Receptor on Th1, Th17, and Regulatory T Cells in Patients with Systemic Lupus Erythematosus or Rheumatoid Arthritis and Its Correlations with Active Disease

P2X7 receptor (P2X7R) is highly expressed on immune cells, triggering the release of cytokines and regulating autoimmune responses. To investigate P2X7R surface expression on T helper (Th) 1, Th17, and regulatory T (Treg) cells in patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA) and correlations with disease activity, 29 SLE and 29 RA patients and 18 healthy controls (HCs) were enrolled. We showed that SLE and RA patients had significantly higher levels of plasma cytokines (IFN-γ, IL-1β, IL-6, IL-17A, and IL-23), frequencies of Th1 and Th17 cells, and expression of P2X7R on Th1 and Th17 than HCs, and the Th17/Treg ratio was significantly increased, whereas Treg cell levels were significantly decreased. The Ca²⁺ influx increase following BzATP stimulation was significantly higher in CD4⁺PBMCs from SLE and RA patients than in HCs. Blood levels of shed P2X7R were increased in SLE and RA patients. Furthermore, 28-joint Disease Activity Score and SLE Disease Activity Index score showed negative correlations with Treg cell levels and positive correlations with Th17/Treg ratio and Th17 cell P2X7R expression. Interestingly, Th17 cell P2X7R expression was closely correlated with IL-1β, C-reactive protein, the erythrocyte sedimentation rate, anticyclic citrullinated peptide Abs, albumin, and C4. These data indicate that increased Th17 cell P2X7R expression is functionally and positively related to disease activity and some inflammatory mediators in SLE and RA patients, and P2X7R could be critical in promoting the Th17 immune response and contributing to the complex pathogenesis of SLE and RA.

The pathogenic role of innate lymphoid cells in autoimmune-related and inflammatory skin diseases

Innate lymphoid cells (ILCs), as an important component of the innate immune system, arise from a common lymphoid progenitor and are located in mucosal barriers and various tissues, including the intestine, skin, lung, and adipose tissue. ILCs are heterogeneous subsets of lymphocytes that have emerging roles in orchestrating immune response and contribute to maintain metabolic homeostasis and regulate tissue inflammation. Currently, more details about the pathways for the development and differentiation of ILCs have largely been elucidated, and cytokine secretion and downstream immune cell responses in disease pathogenesis have been reported. Recent research has identified that several distinct subsets of ILCs at skin barriers are involved in the complex regulatory network in local immunity, potentiating adaptive immunity and the inflammatory response. Of note, additional studies that assess the effects of ILCs are required to better define how ILCs regulate their development and functions and how they interact with other immune cells in autoimmune-related and inflammatory skin disorders. In this review, we will distill recent research progress in ILC biology, abnormal functions and potential pathogenic mechanisms in autoimmune-related skin diseases, including systemic lupus erythematosus (SLE), scleroderma and inflammatory diseases, as well as psoriasis and atopic dermatitis (AD), thereby giving a comprehensive review of the diversity and plasticity of ILCs and their unique functions in disease conditions with the aim to provide new insights into molecular diagnosis and suggest potential value in immunotherapy.

Reduction of circulating innate lymphoid cell progenitors results in impaired cytokine production by innate lymphoid cells in patients with lupus nephritis

Background

Innate lymphoid cells (ILCs) play an essential role in maintaining homeostasis; however, they can also cause chronic inflammation and autoimmune disease. This study aimed to identify the role of ILCs in the pathogenesis of lupus nephritis (LN).

Methods

The percentage of ILCs within the peripheral blood mononuclear cell (PBMC) population and urine of patients with LN (n = 16), healthy controls (HC; n = 8), and disease controls (ANCA-associated vasculitis (AAV; n = 6), IgA nephropathy (IgAN; n = 9), and other glomerular diseases (n = 5)) was determined by flow cytometry analysis. In addition, ILCs were sorted and cultured with plasma from LN patients or HC to elucidate whether the reduced population of CD117⁺ ILCs observed in LN was due to changes in the ILC progenitor population.

Results

The percentage of total ILCs and CD117⁺ ILCs in LN was significantly lower than that in HC. The percentage of cytokine-secreting ILCs was also lower in LN; however, when the disease stabilized, cytokine production was restored to levels similar to those in HC. The increase in the number of exhausted ILCs (cells unable to secrete cytokines) correlated positively with disease activity. When CD117⁺ ILCs were cultured with LN plasma, the number of CD117⁺ ILCs fell, but that of other ILC subsets increased.

Conclusions

The percentage of CD117⁺ ILCs and the capacity of ILCs to secrete cytokines fell as LN severity increased, suggesting that an inflammatory environment of LN induces persistent differentiation and exhaustion of ILCs.